Gas turbine systems are widely utilized in fields such as power generation. A conventional gas turbine system includes a compressor, a combustor, and a turbine. During operation of the gas turbine system, various components in the system are subjected to high temperature flows, which can cause the components to fail. Since higher temperature flows generally result in increased performance, efficiency, and power output of the gas turbine system, the components that are subjected to high temperature flows must be cooled to allow the gas turbine system to operate at increased temperatures.
Various strategies are known in the art for cooling various gas turbine system components. For example, a cooling medium may be routed from the compressor and provided to various components. In the turbine section of the system, the cooling medium may be utilized to cool various turbine components.
Turbine buckets are one example of a hot gas path component that must be cooled. For example, various parts of the bucket, such as the airfoil, the platform, the shank, and the dovetail, require cooling. Thus, various cooling circuits may be defined in the various parts of the bucket, and cooling medium may be flowed through the various cooling circuits to cool the bucket.
Specifically, various strategies are known for cooling the platform. For example, a cooling circuit may be provided in the platform, and cooling medium may be supplied to this cooling circuit to cool the platform. However, various difficulties may be encountered in providing the cooling medium to the platform cooling circuit. For example, one strategy for providing cooling medium to the platform cooling circuit requires that, during casting or otherwise forming the bucket, the core pieces that form the platform cooling circuit and various other cooling circuits are placed in communication with each other. According to this strategy, no post-cast modification of the bucket is required, and the other various cooling circuits may supply cooling medium to the platform cooling circuit. However, placing the platform cooling circuit core and other cooling circuit cores in communication with each other may prevent the various wall thicknesses of the bucket associated with the cores from being independently controlled during casting without overstraining the cores. For example, this may increase the thermally induced strains associated with the cores, and may crack the cores.
Another strategy for providing cooling medium to the platform cooling circuit requires that, after casting of the bucket, a bore hole is drilled from the exterior of the bucket. The bore hole may place the platform cooling circuit in communication with another cooling circuit, such that the other cooling circuit may supply cooling medium to the platform cooling circuit. However, this bore hole must then be plugged from the exterior to prevent cooling medium from escaping. This plugging operation may not be desirable, as it may provide a failure point for the bucket and be relatively unreliable.
Thus, an improved apparatus for cooling a bucket would be desired. Specifically, an improved apparatus for providing cooling medium to a platform cooling circuit in a bucket would be advantageous. Further, a method for forming a bucket with an improved apparatus for providing cooling medium to the platform cooling circuit would be desired.